1,071 research outputs found
UV Completions of Partial Compositeness: The Case for a SU(4) Gauge Group
We present a model of partial compositeness arising as the IR limit of a
SU(4) gauge theory with only fermionic matter. This group is one of the most
promising ones among a handful of possible choices allowing a symmetry breaking
pattern incorporating custodial symmetry and a top partner candidate, while
retaining asymptotic freedom. It is favored for not giving rise to lepto-quarks
or Landau poles in the SM gauge couplings. The minimal UV theory consists of
five hyperfermions in the anti-symmetric representation and three in the
fundamental and anti-fundamental. The IR theory is centered around the coset
SU(5)/SO(5), with top partners in the fundamental of SO(5), giving rise to one
composite fermion of electric charge 5/3, three of charge 2/3 and one of charge
-1/3. Electro-Weak symmetry breaking occurs via top-quark-driven vacuum
misalignment. The top quark mass is generated via the mechanism of partial
compositeness, while the remaining fermions acquire a mass via a standard
quadratic coupling to the Higgs. We compute the top and bottom quark mass
matrix and the Electro-Weak currents of the composite fermions. The model does
not give rise to unacceptably large deviations from the SM Z\to b \bar b decay
width.Comment: 24 pages, 5 figure
LUNES: Agent-based Simulation of P2P Systems (Extended Version)
We present LUNES, an agent-based Large Unstructured NEtwork Simulator, which
allows to simulate complex networks composed of a high number of nodes. LUNES
is modular, since it splits the three phases of network topology creation,
protocol simulation and performance evaluation. This permits to easily
integrate external software tools into the main software architecture. The
simulation of the interaction protocols among network nodes is performed via a
simulation middleware that supports both the sequential and the
parallel/distributed simulation approaches. In the latter case, a specific
mechanism for the communication overhead-reduction is used; this guarantees
high levels of performance and scalability. To demonstrate the efficiency of
LUNES, we test the simulator with gossip protocols executed on top of networks
(representing peer-to-peer overlays), generated with different topologies.
Results demonstrate the effectiveness of the proposed approach.Comment: Proceedings of the International Workshop on Modeling and Simulation
of Peer-to-Peer Architectures and Systems (MOSPAS 2011). As part of the 2011
International Conference on High Performance Computing and Simulation (HPCS
2011
Fermionic UV completions of Composite Higgs models
We classify the four-dimensional purely fermionic gauge theories that give a
UV completion of composite Higgs models. Our analysis is at the group
theoretical level, addressing the necessary (but not sufficient) conditions for
the viability of these models, such as the existence of top partners and
custodial symmetry. The minimal cosets arising are those of type SU(5)/SO(5)
and SU(4)/Sp(4). We list all the possible "hyper-color" groups allowed and
point out the simplest and most promising ones.Comment: 15 pages, 4 tables; V2 Comments and references added. To appear in
JHEP. V3 Coset of type added to the
classificatio
Highly intensive data dissemination in complex networks
This paper presents a study on data dissemination in unstructured
Peer-to-Peer (P2P) network overlays. The absence of a structure in unstructured
overlays eases the network management, at the cost of non-optimal mechanisms to
spread messages in the network. Thus, dissemination schemes must be employed
that allow covering a large portion of the network with a high probability
(e.g.~gossip based approaches). We identify principal metrics, provide a
theoretical model and perform the assessment evaluation using a high
performance simulator that is based on a parallel and distributed architecture.
A main point of this study is that our simulation model considers
implementation technical details, such as the use of caching and Time To Live
(TTL) in message dissemination, that are usually neglected in simulations, due
to the additional overhead they cause. Outcomes confirm that these technical
details have an important influence on the performance of dissemination schemes
and that the studied schemes are quite effective to spread information in P2P
overlay networks, whatever their topology. Moreover, the practical usage of
such dissemination mechanisms requires a fine tuning of many parameters, the
choice between different network topologies and the assessment of behaviors
such as free riding. All this can be done only using efficient simulation tools
to support both the network design phase and, in some cases, at runtime
Mobile Online Gaming via Resource Sharing
Mobile gaming presents a number of main issues which remain open. These are
concerned mainly with connectivity, computational capacities, memory and
battery constraints. In this paper, we discuss the design of a fully
distributed approach for the support of mobile Multiplayer Online Games (MOGs).
In mobile environments, several features might be exploited to enable resource
sharing among multiple devices / game consoles owned by different mobile users.
We show the advantages of trading computing / networking facilities among
mobile players. This operation mode opens a wide number of interesting sharing
scenarios, thus promoting the deployment of novel mobile online games. In
particular, once mobile nodes make their resource available for the community,
it becomes possible to distribute the software modules that compose the game
engine. This allows to distribute the workload for the game advancement
management. We claim that resource sharing is in unison with the idea of ludic
activity that is behind MOGs. Hence, such schemes can be profitably employed in
these contexts.Comment: Proceedings of 3nd ICST/CREATE-NET Workshop on DIstributed SImulation
and Online gaming (DISIO 2012). In conjunction with SIMUTools 2012.
Desenzano, Italy, March 2012. ISBN: 978-1-936968-47-
Anomalous dimensions of potential top-partners
We discuss anomalous dimensions of top-partner candidates in theories of
Partial Compositeness. First, we revisit, confirm and extend the computation by
DeGrand and Shamir of anomalous dimensions of fermionic trilinears. We present
general results applicable to all matter representations and to composite
operators of any allowed spin. We then ask the question of whether it is
reasonable to expect some models to have composite operators of sufficiently
large anomalous dimension to serve as top-partners. While this question can be
answered conclusively only by lattice gauge theory, within perturbation theory
we find that such values could well occur for some specific models. In the
Appendix we collect a number of practical group theory results for fourth-order
invariants of general interest in gauge theories with many irreducible
representations of fermions.Comment: 21 pages, 4 figures, 6 tables V2: Added Table 3,4,5, equation (9) and
various comments in reply to questions and suggestions raised by the two
Referees of SciPost. Two references also added. V3: Typo in footnote 6
corrected. Final version in SciPos
Massless fermionic bound states and the gauge/gravity correspondence
We study the equations of motion of fermions in type IIB supergravity in the
context of the gauge/gravity correspondence. The main motivation is the search
for normalizable fermionic zero modes in such backgrounds, to be interpreted as
composite massless fermions in the dual theory. We specialize to backgrounds
characterized by a constant dilaton and a self-dual three-form. In the specific
case of the Klebanov--Strassler solution we construct explicitly the fermionic
superpartner of the Goldstone mode associated with the broken baryonic
symmetry. The fermionic equations could also be used to search for goldstinos
in theories that break supersymmetry dynamically.Comment: 25 pages. V2: ref. added; V3: ref. adde
Instantons and Toric Quiver Gauge Theories
We show how to construct the general action coupling (multi)instantons to
gauge theories arising from branes probing arbitrary toric singularities. We
give a general set of rules for how to construct such an action given the
knowledge of the superpotential for the gauge theory. The main idea is to
obtain the action by higgsing a theory whose instanton dynamics is known,
namely an orbifold of N=4 super Yang-Mills. We find that the couplings of the
fermionic zero-modes with the holomorphic fields are dictated by the structure
of the superpotential describing the toric singularity. We present explicit
examples such as the Suspended Pinch Point, the Conifold and the first three
del Pezzo's. We perform various checks on these results by further higgsing to
smaller orbifolds and present some applications, including both gauge theory
and stringy instantons.Comment: 42 pages, footnote 2 added, references upgrade
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